Functionalized Maleated Fatty Acids as Non Acidic Fluid Additives

ABSTRACT

Maleated fatty acids that are functionalized with materials such as polyols, alkanolamines and/or alkylene oxides have been discovered to improve the properties of various fluids. In a non-limiting example, functionalized maleated fatty acids having acid numbers less than 10 may improve the lubricity of fuels and lubricants, such as hydrocarbon fuels and lubricants, when added thereto.

TECHNICAL FIELD

The present invention relates to methods and compositions for improving the properties of various fluids, and more particularly relates, in one non-limiting embodiment, to methods and compositions for hydrocarbon fuel lubricity additives made from maleic anhydride and fatty acids.

TECHNICAL BACKGROUND

It is well known that in many internal combustion engines the fuel is also the lubricant for the fuel system components, such as fuel pumps and injectors. Many studies of fuels with poor lubricity have been conducted in an effort to understand fuel compositions that have poor lubricity and to correlate lab test methods with actual field use. The problem is general to diesel fuels, kerosene and gasolines, however, most of the studies have concentrated on the first two hydrocarbon fuels.

Previous work has shown that saturated, monomeric and dimeric, fatty acids of from 12 to 54 carbon atoms used individually give excellent performance as fuel lubricity aids in diesel fuels. A number of other kinds of lubricity additives are also known. Since the advent of low sulfur diesel fuels in the early 1990s, relatively large amounts of these lubricity additives have been used to provide a fuel that does not cause excessive wear of engine parts.

Unfortunately, many commercially available fatty acids and fatty acid blends tend to freeze or form crystals at lower temperatures common during winter weather. The freezing or formation of crystals makes handling of the additives, and particularly their injection into fuel, difficult. Blending the fatty acid with a solvent can lower the freezing point and reduce the crystal formation temperature, or cloud point. However, addition of a solvent may increase cost and preparation complexity.

Some of the fatty acids, fatty acid ammonium salts and fatty acid amides presently used may have the disadvantage of solidifying on storage at low temperatures. Often even at room temperature, crystalline fractions may separate and cause handling problems. Diluting the additives with organic solvents only partly solves the problem, since fractions may still crystallize out from solutions or the solution may gel and solidify. Thus, for use as lubricity additives, the fatty acids, fatty acid ammonium salts and fatty acid amides either have to be greatly diluted or kept in heated storage vessels and added via heated pipework.

Thus, it would be desirable if a way could be discovered to enhance the lubricity of distillate fuels, but the fuels remain homogeneous, clear and flowable at low temperatures. Further, the cold flow properties of middle distillate fuels with the additives should not be significantly adversely affected.

SUMMARY

There is provided, in one non-limiting form, a method of improving the lubricity of a hydrocarbon fuel that involves adding to the hydrocarbon fuel an effective amount of functionalized maleated fatty acid that is an ester, imide and/or amide to improve the lubricity thereof. The functionalized maleated fatty acid is made by a process including reacting an unsaturated fatty acid with an unsaturated compound selected from the group consisting of an unsaturated anhydride, a maleimide, and mixtures thereof. The unsaturated compound may be substituted with a linear or branched alkyl group. This first step gives a maleated fatty acid. Subsequently, the maleated fatty acid is reacted with a multifunctional reactant selected from the group consisting of a polyol, an alkanolamine, an alkylene oxide and mixtures thereof. This gives a functionalized maleated fatty acid that has an acid number less than 10. The functionalized maleated fatty acid may optionally have one of the structures (I) through (IX) shown below.

In addition to, or alternative to the above-noted method for improving the lubricity of a hydrocarbon fuel, it is expected that the functionalized maleated fatty acid may also improve the lubricity of a lubricant, e.g. a motor oil; a transmission fluid, e.g. in an automotive automatic transmission, and in an alcohol, e.g. in methanol and/or ethanol when used as a fuel. Further, it is expected that the functionalized maleated fatty acid may also reduce the corrosivity of these fluids with respect to metals that they come into contact with, as well as to reduce the corrosivity of hydrocarbon fuels.

DETAILED DESCRIPTION

It has been discovered that functionalized maleated fatty acids, which may be esters, imides and/or amides, may improve the properties of certain fluids; for instance they may improve the lubricity and the corrosivity of fuels and lubricants, such as hydrocarbon and/or alcohol fuels and lubricants.

Maleated fatty acids are produced through the reaction of unsaturated fatty acids, such as oleic acid or linoleic acid with maleic anhydride. The resulting maleated fatty acids may be further functionalized with a polyol, e.g. ethylene glycol, glycerol and the like, to make a non-acidic triester; with an alkanolamine to make an imide/amide hybrid; and with an alkanolamine and polyols to make an imide/ester hybrid. The triester, or amide/ester hybrid, are more readily made by alkoxylation with alkanolamine, ethylene oxide (EO) and/or propylene oxide (PO).

The functionalized maleated fatty acid may have a structure of a formula selected from the group (I) through (IX) consisting of:

where:

-   -   R₁ is H or a hydrocarbyl group having 1 to 10 carbon atoms with         zero, one or more double bonds,     -   R₂ is a direct bond or hydrocarbyl group having 1 to 10 carbons         with one or more double bonds,     -   R₃ is —(CH₂CH₂O)_(n)—, or —(CH₂CH(CH₃)O)_(n)—, or combinations         thereof,     -   R₄ is —(CH₂CH₂O)_(n)H, —(CH₂CH(CH₃)O)_(n)H, —CH₂CHOHCH₂OH, or         —CH₂CH₂CH₂CH₂OH or combinations thereof, and     -   n is an integer from 1 to 10, alternatively from 1 to 5.

The functionalized maleated fatty acids herein in one useful, non-limiting embodiment, may be essentially non-acidic, due to all of the carboxylic acid groups being reacted or functionalized, with a multifunctional reactant. In an alternate definition, the acid number of the functionalized maleated fatty acids is less than 10, in another non-limiting embodiment the acid number is less than 5; alternatively it is less than 3. Because these materials are essentially non-acidic or have very low acidity, their ability to contribute to deposit formation tendency of the fluid (e.g. fuel) to which they are added is greatly reduced, and as noted, in some contexts may serve as corrosion inhibitors.

The unsaturated fatty acid used to make the additives described herein may have a weight average molecular weight between about 300 to about 5000 and may be selected from the group consisting of monomeric, dimeric, trimeric crosslinked unsaturated fatty acids, unsaturated fatty acids having from 2 to 30 carbon atoms and mixtures thereof. Specific examples include, but are not necessarily limited to oleic acid, linoleic acid, a-linolenic acid, C10 to C40 unsaturated synthetic dimer fatty acids, unsaturated fatty acids having from 2 to 30 carbon atoms, such as those obtained from the olefin metathesis of fatty acids, arachidonic acid, and mixtures thereof.

The unsaturated compound that is initially reacted with the unsaturated fatty acid is an unsaturated anhydride, such as maleic anhydride or phthalic anhydride; a maleimide, such as maleimide itself or other maleimide, or mixtures thereof. These reactants may be substituted with a linear or branched alkyl group, in one embodiment a lower alkyl group, which is defined herein as having from 1 to 4 carbon atoms. The molar ratio of unsaturated fatty acid to unsaturated compound ranges from about 1:50 independently to about 50:1 in one non-limiting embodiment, in another aspect from about 1:10 independently to about 10:1, alternatively from about 1:2 independently to about 2:1 or in another non-restrictive version from about 1.1:1 independently to about 1:1.1 or equimolar. By “independently” it is meant than any of the lower thresholds may be combined with any of the upper thresholds.

The multifunctional reactants that are reacted with the maleated fatty acid include, but are not necessarily limited to, polyols, alkanolamines, alkylene oxides and mixtures thereof. Suitable polyols include, but are not necessarily limited to glycol, e.g. ethylene glycol and other glycols for instance propylene glycol; glycerol; alkyl phenols; alkyoxylated alkyl phenol; linear or branched alkyl alcohols; each of which may have from 2 to 30 carbon atoms and mixtures thereof. Suitable alkanolamines include, but are not necessarily limited to, ethanolamine, propanolamine, diethanolamine, n-alkylethanolamine, isopropanol amine, diisopropanol amine, 3-amino-1,2-propanediol and mixtures thereof. Suitable alkylene oxides include, but are not necessarily limited to, ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. The molar ratio of maleated fatty acid to multifunctional reactant ranges from about 1:20 to about 20:1 may range from about 1:20 independently to about 20:1; alternatively from about 10:1 independently to about 1:10.

The reactions to make the functionalized maleated fatty acids proceed well without special considerations and are known to those skilled in the art. In general, they may proceed at a temperature range between about 160 to about 260° C. and a pressure range between about 1 to about 10 atm (0.1 to 1 MPa) in the presence of common phenol based antioxidants such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,5-di-tert-butylhydroquinone, polyisobutylene phenol, tocopherol (Vitamin E family) and the like and mixtures thereof. Lewis acid catalysts may be used to improve the reaction rate, but no catalysts are generally used.

The compositions and methods described herein relate to lubricity additive compositions for distillate fuels, but also may be useful in products from resid. In the context herein, distillate fuels include, but are not necessarily limited to diesel fuel, kerosene, gasoline middle distillate fuel, and the like. They may also be used in heavy fuel oil. It will be appreciated that distillate fuels include blends of conventional hydrocarbons meant by these terms with oxygenates, e.g. alcohols, such as methanol, ethanol, and other additives or blending components presently used in these distillate fuels, or that may be used in the future. They may also be used in relatively pure alcohols, for instance when an alcohol such as methanol is pumped as a hydrate inhibitor or when ethanol and/or methanol are used as fuels. It is also expected that the functionalized maleated fatty acids will serve as corrosivity preventers and lubricity enhancers in biofuels. In one non-limiting particular embodiment, the methods and compositions herein relate to low sulfur fuels, which are defined as having a sulfur content of 0.2% by weight or less, and in another non-limiting embodiment as having a sulfur content of about 0.0015 wt. % or less—such as the so-called “ultra low sulfur” fuels. Particularly suitable hydrocarbon fuels herein include, but are not necessarily limited to, diesel and kerosene, and in one non-restrictive version, ultra low sulfur diesel (ULSD) fuels. However, they also may be used for fuels having sulfur contents higher than this.

As previously noted, the functionalized maleated fatty acids described herein may also be used as corrosivity improvers for the fuels described above, for instance when these fuels come into contact with metal, particularly, but not limited to, iron alloys, particularly the various commonly used steel alloys. Besides use as lubricity enhancers and/or corrosivity improvers for the fuels described above, the functionalized maleated fatty acids may function as corrosion inhibitors or lubricity enhancers in other fluids including, but not necessarily limited to, lubricants, such as motor oil, transmission fluids, cutting fluids, and the like.

In one non-limiting embodiment of the methods and compositions, the lubricity additive in the total fuel should at least be an amount to improve the lubricity of the fuel as compared to an identical fuel absent the additive. Alternatively, the amount of additive may range from about 25 independently to about 3000 ppm, and in an alternate embodiment, the lower threshold may be about 25 ppm and the upper threshold may independently be about 200 ppm and in one non-limiting embodiment from about 50 independently to about 150 ppm.

When the functionalized maleated fatty acid additives are used as corrosion inhibitors, for instance in a hydrocarbon fuel or another fluid as previously described, the amount of additive should be that effective to reduce the corrosivity of the fluid as compared to an identical fuel absent the additive. In one non-limiting embodiment, the amount may range from about 1 independently to about 100 ppm, alternatively from about 1 independently to about 10 ppm.

Other, optional components may be added independently to the fluids being treated. In non-limiting embodiments these may include, but are not necessarily limited to, detergents, pour point depressants, cetane improvers, dehazers, cold operability additives (e.g. cold flow improvers), conductivity improvers, other corrosion inhibitors, stability additives, demulsifiers, biocides, dyes, and mixtures thereof. In another non-limiting embodiment of the methods and compositions herein, water is explicitly absent from the inventive composition.

The invention will now be illustrated with respect to certain Examples which are not intended to limit the invention, but instead to more fully describe it.

Examples 1-5 Preparation of Functionalized Maleated Fatty Acid Products Example 1

The preparation of maleated fatty acid: In a typical reaction, oleic acid (100 g) and maleic anhydride (25 g) were charged into a 250 ml 3-neck flask under nitrogen. The mixture was heated sequentially up to 240° C. for 30 hrs until the reaction was completed. The reaction was monitored by FT-infrared spectroscopy (FT-IR) as is known to those skilled in the art. The final product was diluted by aromatic solvent to a concentration of 90% active and marked as Example 1.

Above is a representative structure of Example 1 material.

Example 2

Oleic acid (100.1 g) and maleic anhydride (25.3 g) were mixed in a 3-neck flask. The mixture was heated sequentially up to 240° C. until the reaction is completed as monitored by FT-IR. The reaction mixture was first cooled to room temperature, and then ethanolamine (38.0 g) was added drop-wise while stirring. After the addition was completed, the reaction temperature was first set at 80° C., and then raised to 180° C. sequentially in 2 hours. The reaction process was monitored by FT-IR and acid number analysis. A second batch of ethanolamine (6.0 g) was added after 8 hrs reaction time. The reaction was stopped when the acid number is below 3. The final product was diluted with aromatic solvent to a concentration of 80% active and marked as Example 2.

Above is a representative structure of Example 2.

Example 3

Linoleic and oleic acid mixture (100.0 g) and maleic anhydride (25.0 g) were mixed in a 3-neck flask. The mixture was heated sequentially up to 240° C. until the reaction is completed as monitored by FT-IR. The reaction mixture was first cooled to room temperature, and then ethanolamine (15.6 g) was added dropwise while stirring. After the addition was completed, the reaction temperature was first set at 70° C., and then raised to 120° C. sequentially in 4 hours. The reaction process was monitored by FT-IR. Ethylene glycol (22.1 g) was added after the amines are consumed. The temperature was raised to 185° C. and water was removed as a by-product via a Dean-Stark trap. After the acid number reached 20, a second batch of ethylene glycol (4.6 g) was added to drive the acid number further down. The reaction was stopped when the acid number was below 5. The final product was diluted with aromatic solvent to a concentration of 90% active and marked as Example 3.

Above are representative structures of Example 3.

Example 4

Pre-distilled maleated oleic acid (297.7 g) and ethylene glycol (142.6 g) were charged into a 500 mL 3-neck flask that is equipped with a Dean-Stark trap. The mixtures were heated up to 200° C. to remove water. The reaction process was monitored by FT-IR and acid number. After the acid number reach 20, a second batch of ethylene glycol (6.0 g) was added and heated at 185° C. with N₂ purging. The final reaction was stopped when the acid number is less than 10. The final product was collected and marked as Example 4.

Above is a representative structure of Example 4.

Example 5

Pre-distilled maleated oleic acid (224.1 g) and ethylene glycol (36.1 g) were charged into a par reactor. N,N-dimethyl benzylamine (1.7 g) was added as a base catalyst. The mixture was ethoxylated at 115° C. till the acid number is less than 2. The final product was collected and marked as Example 5.

Above is a representative structure of Example 5 (R₁=—(CH₂CH₂O)_(n)H, where n=1˜5).

Examples 6-11 Effectiveness of Ex. 1-5 Materials as Lubricity Improvers

The lubricity improvers' effectiveness was examined on a High Frequency Reciprocating Rig (HFRR) in accordance with ASTM D6079. The results are reported in Table I as mean Wear Scar Diameter (WSD) in micrometers. The lower the WSD, the more effective the lubricity improver is. It may be seen that the products from all Examples 1-5 gave improved lubricity, whereas the material from Example 5 gave the lowest WSD result.

TABLE I Results of Lubricity Improver Tests From Dosage WSD Ex. Example Active % (ppm) Fuel (μm) 6 Blank — — — 593 7 1 90 100 Western ULSD 538 8 2 80 100 Western ULSD 500 9 3 100 100 Western ULSD 444 10 4 100 100 Western ULSD 411 11 5 100 100 Western ULSD 341

Examples 12-14 Corrosion Inhibition Results

The corrosion inhibition property of the above samples was examined with a standard NACE spindle test (TM-017201) for both gasoline and diesel fuel. The results are reported in a relative scale of A-E with which a rating of “A” means no corrosion while a rating of “E” means more than 75% of the surface is rusted. The results are shown in the Table II.

TABLE II Corrosion Inhibition Results Gasoline Diesel Fuel Dose Dose Additive Activity (%) (ppm) Rating (ppm) Rating Blank D D Ex. 3 100 3 B 3 B+ Ex. 4 60 3 D 3 B 4.5 B+ 6 B+ Ex. 5 60 3 D 3 B 4.5 B 6 B 6 B+

It is to be understood that the invention is not limited to the exact details of monomers, reaction conditions, proportions, etc. shown and described, as modifications and equivalents will be apparent to one skilled in the art. Accordingly, the invention is therefore to be limited only by the scope of the appended claims. Further, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific combinations of unsaturated fatty acids, unsaturated compounds, multifunctional reactants, reactant proportions, reaction conditions, molecular weights, dosages and the like falling within the claimed parameters, but not specifically identified or tried in a particular method, are anticipated to be within the scope of this invention.

The terms “comprises” and “comprising” in the claims should be interpreted to mean including, but not limited to, the recited elements.

The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For instance, the method may consist essentially of or consist of reacting an unsaturated fatty acid with an unsaturated compound selected from the group consisting of an unsaturated anhydride, a maleimide, and mixtures thereof where the unsaturated compound may be substituted with a linear or branched alkyl group, which reacting gives a maleated fatty acid. The method may optionally additionally consist essentially of or consist of reacting the maleated fatty acid with a multifunctional reactant selected from the group consisting of a polyol, an alkanolamine, an alkylene oxide and mixtures thereof to give a functionalized maleated fatty acid that has an acid number less than 10, where the reactants are as described in the claims. 

What is claimed is:
 1. A method of improving the lubricity of a fuel, the method comprising: adding to the fuel an effective amount of a functionalized maleated fatty acid that is an ester, imide, and/or amide to improve the lubricity thereof.
 2. The method claim 1 where the functionalized maleated fatty acid is made by a process comprising: reacting an unsaturated fatty acid with an unsaturated compound selected from the group consisting of an unsaturated anhydride, a maleimide, and mixtures thereof where the unsaturated compound may be substituted with a linear or branched alkyl group, which reacting gives a maleated fatty acid; reacting the maleated fatty acid with a multifunctional reactant selected from the group consisting of a polyol, an alkanolamine, an alkylene oxide and mixtures thereof to give a functionalized maleated fatty acid that has an acid number less than
 10. 3. The method of claim 1 where the functionalized maleated fatty acid has a structure selected from the group consisting of:

where: R₁ is H or a hydrocarbyl group having 1 to 10 carbon atoms with zero, one or more double bonds, R₂ is a direct bond or hydrocarbyl group having 1 to 10 carbons with one or more double bonds, R₃ is —(CH₂CH₂O)_(n)—, or —(CH₂CH(CH₃)O)_(n)—, or combinations thereof, R₄ is —(CH₂CH₂O)_(n)H, —(CH₂CH(CH₃)O)_(n)H, —CH₂CHOHCH₂OH, or —CH₂CH₂CH₂CH₂OH or combinations thereof, and n is an integer from 1 to
 10. 4. The method of claim 3 where the n is an integer from 1 to
 5. 5. The method of claim 1 where the functionalized maleated fatty ester/imide/amide has an acid number less than
 5. 6. The method of claim 2 where the effective amount of functionalized maleated fatty acid added to the fuel ranges from about 1 to about 3000 ppm.
 7. The method of claim 2 where the unsaturated fatty acid has a weight average molecular weight between about 300 to about
 5000. 8. The method of claim 6 where the unsaturated fatty acid is selected from the group consisting of monomeric, dimeric, trimeric crosslinked unsaturated fatty acids and mixtures thereof.
 9. The method of claim 2 where the molar ratio of unsaturated fatty acid to unsaturated compound ranges from about 1:50 to about 50:1.
 10. The method of claim 2 where the molar ratio of maleated fatty acid to multifunctional reactant ranges from about 1:20 to about 20:1.
 11. The method of claim 2 where: the unsaturated fatty acid is selected from the group consisting of oleic acid, linoleic acid, a-linolenic acid, arachidonic acid, C10 to C40 unsaturated synthetic dimer fatty acids, dimer acid, unsaturated fatty acids having from 2 to 30 carbon atoms, and mixtures thereof; the polyol is selected from the group consisting of glycol, glycerol, alkyl phenols, alkyoxylated alkyl phenol, linear or branched alkyl alcohols, the polyol having from 2 to 30 carbon atoms and mixtures thereof; the alkanolamine is selected from the group consisting of ethanolamine, propanolamine, diethanolamine, n-alkylethanolamine, isopropanol amine, diisopropanol amine, 3-amino-1,2-propanediol and mixtures thereof; and the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide and mixtures thereof.
 12. A method of improving the properties of a fluid selected from the group consisting of: reducing the corrosivity of a fluid selected from the group consisting of a fuel, a lubricant, a motor oil, a transmission fluid, and an alcohol; and improving the lubricating properties of a lubricant, a motor oil, a transmission fluid, and an alcohol; the method comprising adding to the fluid an effective amount of a functionalized maleated fatty acid that is an ester, imide, and/or amide to either improve the lubricity and or reduce the corrosivity thereof.
 13. The method of claim 12 where the functionalized maleated fatty acid is made by a process comprising: reacting an unsaturated fatty acid with an unsaturated compound selected from the group consisting of an unsaturated anhydride, a maleimide, and mixtures thereof where the unsaturated compound may be substituted with a linear or branched alkyl group, which reacting gives a maleated fatty acid; reacting the maleated fatty acid with a multifunctional reactant selected from the group consisting of a polyol, an alkanolamine, an alkylene oxide and mixtures thereof to give a functionalized maleated fatty acid that has an acid number less than
 10. 14. The method of claim 12 where the method is for reducing the corrosivity of a fuel, and the effective amount of functionalized maleated fatty ester/imide/amide ranges from about 1 to about 100 ppm.
 15. The method of claim 12 where the functionalized maleated fatty acid has a structure selected from the group consisting of:

where: R₁ is H or a hydrocarbyl group having 1 to 10 carbon atoms with zero, one or more double bonds, R₂ is a direct bond or hydrocarbyl group having 1 to 10 carbons with one or more double bonds, R₃ is —(CH₂CH₂O)_(n)—, or —(CH₂CH(CH₃)O)_(n)—, or combinations thereof, R₄ is —(CH₂CH₂O)_(n)H, —(CH₂CH(CH₃)O)_(n)H, —CH₂CHOHCH₂OH, or —CH₂CH₂CH₂CH₂OH or combinations thereof, and n is an integer from 1 to
 10. 16. The method of claim 15 where the n is an integer from 1 to
 5. 17. The method of claim 12 where the functionalized maleated fatty ester/imide/amide has an acid number less than
 5. 18. The method of claim 12 where the effective amount of functionalized maleated fatty acid added to the fuel ranges from about 1 to about 3000 ppm.
 19. The method of claim 13 where the unsaturated fatty acid has a weight average molecular weight between about 300 to about 5000 and where the unsaturated fatty acid is selected from the group consisting of monomeric, dimeric, trimeric crosslinked unsaturated fatty acids and mixtures thereof.
 20. The method of claim 13 where the molar ratio of unsaturated fatty acid to unsaturated compound ranges from about 1:50 to about 50:1.
 21. The method of claim 13 where the molar ratio of maleated fatty acid to multifunctional reactant ranges from about 1:20 to about 20:1.
 22. The method of claim 13 where: the unsaturated fatty acid is selected from the group consisting of oleic acid, linoleic acid, a-linolenic acid, arachidonic acid, C10 to C40 unsaturated synthetic dimer fatty acids, unsaturated fatty acids having from 2 to 30 carbon atoms, and mixtures thereof; the polyol is selected from the group consisting of glycol, glycerol, alkyl phenols, alkyoxylated alkyl phenol, linear or branched alkyl alcohols, the polyol having from 2 to 30 carbon atoms and mixtures thereof; the alkanolamine is selected from the group consisting of ethanolamine, propanolamine, diethanolamine, n-alkylethanolamine, isopropanol amine, diisopropanol amine, 3-amino-1,2-propanediol and mixtures thereof; and the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. 